“The e-cigarette market is rapidly evolving and research on the huge variety of products on the market, what they emit and what their health impacts are, lags behind.

“What we do know is that e-cigarettes do not emit the thousands of constituents delivered in tobacco smoke, 70 of which are known carcinogens. Instead e-cigarettes emit a vapourised solution principally of propylene glycol or glycerine, water and flavours, usually with nicotine. Whilst the WHO report concludes that e-cigarettes use ’produces lower exposures to toxicants than combustible products’ I believe that this is an understatement. We can be confident that e-cigarette use results in much lower exposure to toxins for users.

“Although e-cigarette vapour may be an irritant to people in close proximity to the e-cigarette user, there is no evidence of harm from other people inhaling e-cigarette vapour unlike the known risks of second hand cigarette smoke. There is also as yet no evidence that e-cigarettes are renormalizing smoking.

“Based on their analysis, the WHO proposes a range of regulations for e-cigarettes and my concern is that these will deter smokers from trying to use them. Cigarette smoking is so uniquely dangerous that anything we can do to encourage smokers to stop should be welcomed. In the UK whilst we have achieved remarkable reductions in smoking over recent decades, smoking is now concentrated among our most disadvantaged groups in society, for whom I think e-cigarettes could be a game changer.”